> On Aug 17, 2022, at 14:21, Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>
> The pmd_huge() is used to validate if the pmd entry is mapped by a huge
> page, also including the case of non-present (migration or hwpoisoned)
> pmd entry on arm64 or x86 architectures. Thus we should validate if it
> is present before making the pmd entry old or getting young state,
> otherwise we can not get the correct corresponding page.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> mm/damon/vaddr.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 3c7b9d6..1d16c6c 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -304,6 +304,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
>
> if (pmd_huge(*pmd)) {
> ptl = pmd_lock(walk->mm, pmd);
> + if (!pmd_present(*pmd)) {
Unluckily, we should use pte_present here. See commit c9d398fa23788. We can use
huge_ptep_get() to get a hugetlb pte, so it’s better to put the check after
pmd_huge.
Cc Mike to make sure I am not missing something.
Muchun,
Thanks.
> + spin_unlock(ptl);
> + return 0;
> + }
> +
> if (pmd_huge(*pmd)) {
> damon_pmdp_mkold(pmd, walk->mm, addr);
> spin_unlock(ptl);
> @@ -431,6 +436,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> if (pmd_huge(*pmd)) {
> ptl = pmd_lock(walk->mm, pmd);
> + if (!pmd_present(*pmd)) {
> + spin_unlock(ptl);
> + return 0;
> + }
> +
> if (!pmd_huge(*pmd)) {
> spin_unlock(ptl);
> goto regular_page;
> --
> 1.8.3.1
>
>
